1. Field of the Invention:
This invention relates to a temperature sensor using electrical conductors whose electrical resistance varies with temperature and more particularly to such a temperature sensor suitable for temperature measurement in a varying magnetic field.
2. Description of the Prior Art:
The recent advances in the development of superconducting magnets and the like have led to the use of strong magnetic fields in various disciplines. For ensuring safety and reducing energy consumption when using a superconducting magnet, it is important to monitor the temperature throughout the magnet. The thermometers used in the cryogenic environments in which superconducting magnets operate are generally temperature sensors utilizing the change in resistance of a conductor with change in temperature. Although deviations arise in the readings produced by temperature sensors of this type owing to the effect of the magnetic field on the conductor, it is in principle possible to correct individual temperature sensors for deviation by calibrating them in a static magnetic field. The measurement of temperature in a magnetic field has therefore been conducted by first ascertaining the correction value required for the temperature sensor in a magnetic field of known intensity and then using the correction value to correct the measured value to thereby determine the actual temperature in the environment concerned.
Since this method of temperature method requires the corrections to be carried out individually, however, it is troublesome and reduces the efficiency of the temperature measurement work. In addition, error introduced in the course of determining the correction value detracts from the measurement accuracy.
Moreover, the prior art temperature sensor cannot be used in the new fields of application that have developed as advances in superconducting technology have made it possible for superconducting magnets to produce magnetic fields that vary at several to several tens of Hz. This is because the resistance of the temperature sensor conductor varies synchronously with the frequency of the magnetic field, making it impossible to measure temperature accurately and to carry out the conventional correction.
It is therefore an object of the present invention to provide a temperature sensor which is hardly affected by magnetic field and is therefore capable of measuring temperature with high accuracy in a varying magnetic field.